1. Field of the Invention
The present invention relates to a recording apparatus for use in information processing apparatuses including a printer, a copy machine, a computer, a word processor, and the like. In particular, this invention relates to a recording apparatus capable of recording high quality images on various kinds of recording mediums.
2. Description of the Related Art
There has been known a recording apparatus which has a plurality of functions so that it can serve as a printer, a copy machine and a facsimile apparatus. There has also been known another recording apparatus which can be used as an output device for a composite electronic apparatus including a computer and a word processor, and can also be used an output device for a work station. Each of these recording apparatus is fabricated so that it can be used to record various kinds of images (characters, marks or the like) on a recording medium such as a recording paper or a thin plastic plate, in accordance with image data provided to the recording apparatus. In fact, the aforesaid recording apparatus may be in any one of the following forms: an ink-jet printer, a wire-dot printer, a thermal printer and a laser beam printer.
Further, in a serial type recording apparatus capable of carrying out a recording process while at the same time performing a main scanning in a direction intersecting a recording medium transporting direction (sub-scanning direction), the recording process (main scanning) is effected by a recording means (a recording head) moving along the recording medium. After the recording along one line on the recording medium is finished, a predetermined amount of paper conveying is performed (which is a pitch transportation acting as a sub-scanning). Subsequently, the recording process (main scanning) along the next line on the same recording medium is performed, thereby completing a desired recording in a desired range on the recording medium by repeating the above recording process. On the other hand, in a line-type recording apparatus in which the recording is performed only by carrying out the sub-scanning of the recording medium, the recording medium is at first set in a predetermined recording position. Then, while the recording along one line is continuously performed as one operation, a predetermined amount of paper conveying (pitch transportation) is performed, thereby completing a desired recording in a desired area on the recording medium.
Among the aforementioned recording apparatus, an ink-jet recording apparatus is formed in such a construction that ink is discharged from a recording means (recording head) towards a recording medium, thereby effecting a desired recording. In fact, such kind of a recording head can be easily made compact, and it is possible to record fine images at a high speed. Therefore, it is possible to use a plain paper as a recording medium without having to perform any special treatment. Further, using an ink-jet recording apparatus makes it possible to reduce running cost, and since an ink-jet recording apparatus employs a non-impact printing manner, an operation noise is low. In addition, another advantage obtainable by employing an ink-jet recording apparatus is that it is possible to use various kinds of inks (such as color inks), thereby making it easy to record various color images.
In fact, using an ink-jet recording apparatus makes it possible to realize the recording of high quality images, by keeping small a distance between a recording head and a recording medium. FIG. 6 is a cross sectional view schematically showing a conventional ink-jet recording apparatus. In FIG. 6, reference numeral 132 represents a recording head for discharging ink onto the recording surface of a recording sheet S, thereby effecting a desired recording on the recording sheet. Reference numeral 123 is a platen for guiding the back surface of the recording sheet S in a position opposite to the recording head 132. Reference numeral 121 represents a transporting roller for contacting the back surface of the recording medium S and thus transporting the same in an area upstream of the recording head 132 along the recording sheet transporting direction. Reference numeral 122 represents a pinch roller which is driven by the transporting roller 121 and thus rotates in contact with the recording surface of the recording sheet S. Reference numeral 141 represents a paper discharge roller for discharging, from the recording apparatus, a recording sheet on which a desired recording has been performed by the recording head 132. Reference numeral 142 represents a driven roller which is rotated by the paper discharge roller 141. Actually, the conventional ink-jet recording apparatus is constructed in such a manner that the recording sheet S may be pressed against the platen 123 by deviating the pinch roller 122 (with respect to the transporting roller 121) towards the downstream side in the recording sheet transporting direction. In this way, it is possible to maintain a small distance or a gap between the recording head 132 and the recording sheet S.
However, the above-described conventional ink-jet recording apparatus has been found to have the following problems. Namely, when a recording sheet is to be fed for recording by the recording head, it is necessary to perform an inclination correction (registration) on the front edge of the recording sheet by bringing the recording sheet to a nip position between the transporting roller 121 and the pinch roller 122. Particularly, in recent years, although there have been produced many kinds of recording mediums which can be used in recording apparatus, some of them fail to be smoothly nipped at the nip position between the two rollers. As a result, some recording sheets will still be inclined or canted, which causes an insufficient nipping of the front edge of the recording sheet. Consequently, it is difficult to transport the recording sheet in a proper manner.
Further, when the rear edge of a recording sheet is deviated from the nip position between the transporting roller 121 and the pinch roller 122, the recording sheet will be kicked away, resulting in a problem that the recording sheet will be transported in a larger amount than predetermined, thus producing a disturbed image.
FIGS. 7A and 7B are explanatory views showing kicking-away of the rear end of the recording sheet. As shown in FIG. 7A, when a recording sheet is being transported, a pressing force for nipping the recording sheet is acting at the nip position between the transporting roller and the pinch roller. When the rear end of the recording sheet is being moved from the nip position, there will be another force sending the recording sheet forward in the recording sheet transporting direction, as shown in FIG. 7B. As a result, the recording sheet will be undesirably sent forward by a larger amount than desired, producing a disturbed image in the rear area of the recording sheet. Here, an amount of kicking-away will be different from one recording sheet to another, depending on the type of each recording sheet, particularly the thickness of each recording sheet. Moreover, even the recording sheets of the same type will still have different kicking-away amounts. For this reason, it is difficult to perform an exact control of the kicking-away amount of each recording sheet, even if such an amount is predicted in advance and the recording operation is controlled.